Boot upper



FIG. 1 is a right side elevation view of a boot upper showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a rear elevational view thereof; and,

FIG. 5 is a front elevational view thereof.

The broken line showing of a shoe sole and laces in FIGS. 1-5 is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a boot upper, as shown and described. 